1. Field of the Invention
The present invention relates to a composition for forming a conductive film, and more particularly, to a composition for forming a conductive film to be coated on the outer surface of a panel of a cathode ray tube (CRT), the composition having an improved bonding property between the components thereof and a dispersing property of the components thereof, a method for preparing the same, and a CRT employing the conductive film formed using the composition to thereby improve a contrast characteristic and film properties such as film hardness or chemical/mechanical film stability.
2. Description of the Related Art
An image is formed on a CRT by an electron beam emitted from an electron gun, which is selectively deflected by a deflection yoke according to landing positions and lands on a phosphor layer formed on the inner surface of a panel to thus excite the phosphor causing it to luminesce.
A curved panel having a predetermined curvature is typically used as the panel of a CRT. Although curved panels are disadvantageous in view of attaining a high-quality image, due to severe glare and image distortion at the peripheral portion thereof, they are still chiefly used as panels for CRTs due to technical difficulties in manufacturing flat panels.
However, due to recent advances in the technologies used to manufacture flat panels, existing curved panels are being replaced by flat panels having a curvature close to infinity.
A panel having a large curvature, that is, a nearly flat panel, can realize a clean image by suppressing glare due to reflection of external light, reduce eye fatigue and eliminate distortion of an image.
As an example of a flat panel, a panel shown in FIG. 1, whose internal and external surfaces are both completely flat, has been proposed. In a CRT employing such a flat panel, an image formed on the central portion of the panel appears to recede inwardly.
To overcome this problem, as shown in FIG. 2, a flat panel having a completely flat external surface and a curved internal surface having a predetermined curvature has been proposed.
However, according to this flat panel, it is difficult to attain a uniform image due to different transmittances between the central portion and the peripheral portion of the panel, which is caused by a difference in the thicknesses of the central and peripheral portions. Also, in the case of employing a general dark tint panel or a semi-tint panel having a transmittance of about 40xcx9c50% as the flat panel, the difference between the transmittances of the central portion and the peripheral portion of the panel becomes bigger.
Therefore, the present invention is for forming a conductive film having excellent contrast characteristics and improved film properties to overcome the above-mentioned problems.
To solve the above problems, it is an objective of the present invention to provide a composition having a property of improved bonding between the components thereof and a property of improved dispersion of the components thereof, for forming a conductive film to be coated on the outer surface of a panel of a CRT.
It is another objective of the present invention to provide a method for preparing a composition for forming the conductive film.
It is still another objective of the present invention to provide a cathode ray tube having excellent contrast characteristics and film properties due to the use of a conductive film formed using the composition.
Accordingly, to achieve the first objective, there is provided a composition for forming a conductive film to be coated on the outer surface of a panel of a cathode ray tube, the composition including conductive black pigment particles, pigment particles for adjusting the transmittance of light at different wavelengths, a conductive polymer, and at least one silica selected from the group consisting of siliconalkoxide and oligomers thereof, wherein the conductive black pigment particles and pigment particles for adjusting the transmittance of light at different wavelengths are bonded to a network of an organic-inorganic composite sol while being uniformly dispersed in the network.
To achieve the second objective, there is provided a method of preparing a composition for forming a conductive film to be coated on the outer surface of a panel of a cathode ray tube, the method including the steps of (a) dispersing conductive black pigment particles, at least one silica selected from the group consisting of silicon alkoxide and oligomers thereof, and a conductive polymer in an organic solvent mixture, to prepare an organic-inorganic composite sol, (b) dispersing pigment particles for adjusting the transmittance of light at different wavelengths, a dispersing agent and a conductive polymer in an organic solvent mixture to prepare a pigment composition, and (c) mixing the organic-inorganic composite sol and the pigment composition and subjecting to the mixture to ultrasonic dispersion.
To achieve the third objective, there is provided a cathode ray tube including a panel, and a conductive film formed on the outer surface of the panel using the composition according to the present invention.